Anti-swing crane



I Spt. 17, 1957 Filed" Oct. 27, 1953 R. c. GOERTZ ANTI-SWING CRANE 2 Sheets-Sheet 1 INVENTOR. RAYMOND c. GOERTZ 4&4

ATTORNEY "Sept: 17, 1957 Filed 091.. 27, 1953 R. c. GQERTZ ANTI-SWING CRANE 2 Sheets-Sheet mmvron RAYMOND CGOERTZ ATTORNEY United States Patent 7 2,806,610 ANTI-SWING CRANE Raymond C. Goertz, Downers Grove, Ill., assignor to the United States of America as represented by the Unit-ed States Atomic Energy Commission Application October 27, 1953, Serial No. 388,707

7 Claims. (Cl. 212-131) This invention relates to an apparatus for remotely positioning objects and more particularly an apparatus employing a cable or other flexible element for suspending objects to be transported from one place to another.

When a crane with a cable is used to transport an object from one place to another, the object has a tendency to swing after horizontal motion of the crane has been started or stopped. If the object being transported is thermally or radioactively hot, it may not be feasible for a rigger to stop the swinging by handling the object or the cable in the vicinity of the object. A special device that will reach down'toward the object to dampen the swing may be costly and complicated.

I propose to prevent or reduce the swinging of the object on the cable by specially controlling the movement of the crane itself. According to the present invention, the tendency of the cable to swing on starting or stopping of the horizontal movement of the crane is used to generate a signal that modifies the movement of the crane.

In the drawing: 1

Figure 1 is a diagrammatic and perspective view of a crane and controls for moving the crane and inhibiting swinging of the cable hanging from the crane;

' Figure 2 is a perspective and diagrammatic view of a modified form of device for generating a signal from the swing of the cable.

In Figure 1, reference character 10 designates a crane that comprises a carriage 11, a plurality of wheels 12, and a cable 13 from which an object 14 is suspended. The wheels 12 ride on flanges of beams 15 which constitute horizontal rails for the crane. The cable 13 may be shortened or lengthened by means of a drum 16 of which it is trained and which is controlled by means of a motor 17 mounted on the carriage 11. The carriage 11 is shifted along the rails 15 by means of a rack 18 secured to one rail 15 and a pinion 19 meshing with the rack 18. The pinion is driven by a servo-motor 20 acting through reducing gears 20a, 20b, 20c, and 20d. The servo-motor is driven from an amplifier 21 connected thereto by a line 22.

The amplifier 21 receives signals that cause the motor 20 to be driven from four different sources; a position control 23, a position transducer 24, tachometer generator 25, and, according to the present invention, a swingangle transducer 26.

In the form of the apparatus illustrated in Figure 1, the position control 23 and the position transducer 24 take the form of otentiometers. The position control 23 comprises a spiral resistor 28, a movable arm 27 slidable along the resistor 28, and a control knob 29 for positioning the arm 27. The position transducer 24 comprises a spiral resistor 30 and a movable arm 31 slidable along the resistor 30. The arm 31 is connected with the pinion 19 through reducing gears 32 and 32a so as to be angularly shifted along the resistor 30 in accordance with movement of the carriage 11 along the rails 15. The ends of the position-control resistor 28 are connected through lines 33 and 34 with a battery 35, which is connected at an intermediate point to a ground 36. Lines 37 and 38 connect Patented Sept. 17, 1957 the ends of the position-transducer resistor 30 with the battery 35. The position-control arm 27 is connected by a line 39 with the amplifier 21. The position-transducer arm 31 is connected through a line 40 with the amplifier 21. The tachometer generator 25 is driven by the servomotor 20 and is connected to ground as indicated at 41 and with the amplifier through a line 42.

According to the present invention, the swing-angle transducer, which is the embodiment illustrated in Figure 1 takes the form of a potentiometer, is controlled by means of a slotted follower 43 which straddles the cable 13 so as to follow it when it swings as indicated by the full-line and dotted-line positions illustrated in Figure l. The follower 43 is mounted by means of support 43a so as to be movable bodily with the carriage 11 as it goes along the rails 15 and to swing about a horizontal axis as the cable 13 swings. The follower 43 carries a shaft 44 which contains the axis about which the follower is mounted to swing and connects the follower with a movable arm 45 which forms part of the swing-arm transducer 26. The arm 45 slides over a spiral resistor 46 which also forms part of the transducer 26 and is connected with the amplifier 21 through a line 47. The ends of the resistor 46 are connected with the battery 35 through lines 33 and 34 through lines 48 and 49 which are connected to the lines 33 and 34.

When the carriage 11 is in a fixed position and object 14 suspended by cable 13 is in a steady state, the position control 23 and the position transducer 24 are in a balanced condition, their respective moveable arms 27 and 31 contacting their respective resistors 28 and 30 so that signals of equal potential are transmitted to the amplifier 21. The slotted follower 43 is in a vertical position causing the arm 45 to be at the central resistive point of resistor 46 so that no signal is being transmitted therefrom to the amplifier. Since the motor is not operating the tachometer generator 25 is not rotating and no signal is being transmitted therefrom. When the object 14 suspended from the carriage 11 and the cable 13 is to be shifted to a new position, the control knob 29 is twisted to a position representative of such new position. This causes the signal transmitted to the amplifier 21 through the line 39 to be different from that transmitted from the position transducer '24 through the line 40, and so the amplifier drives the servo-motor 20 in the appropriate direction for bringing the carriage 11 to the new selected position. As the servo-motor 20 rotates, it causes the tachometer generator 25 to rotate, sending a signal through the line 42 to the amplifier 21, causing the amplifier to steady the servo-motor 20 and to prevent hunting when the carriage 11 reaches the position for Whichthe position control 23 is set.

When the carriage 11 commences its movement toward the new desired position determined by the position control 23, there is a tendency for the cable 13 to lag behind or, in other words, to assume a definite angle to the vertical. This lag angle is transmitted by the follower through the shaft 44 to the movable arm 45 of the swingangle transducer 26. Thus, a signal is transmitted to the amplifier 21 through the line 47, which signal acts to cause the amplifier 21 to reduce the speed of the servo-motor or rather to make it reach its normal traveling speed more slowly. Thus the tendency for the cable 13 to lag behind is reduced. When the carriage 11 approaches the position determined by the control 23, the relation of the signals transmitted to the amplifier through the lines 39 and 40 by the position control 23 and the position transducer 24 changes so as to slow down the servo-motor and thus to diminish the speed of the carriage 11. This causes the cable 13 to tend to move ahead of the carriage and thus to make an angle with the vertical in the direction opposed to that occurring in starting. Thus the follower 43 causes the arm 45 of the swing-angle transducer 26 to assume a completely diiferent position with respect to the resistor 46, and the signal transmitted from the arm 45 through the line 47 to the amplifier 21 isreversed in algebraic sign so as to alter the slowing-down process of the carriage 11 as otherwise determined by the relationship of the signals transmitted from the position control 23 and the position transducer 24. This means that the tendency for the cable 13 to move ahead is reduced, and the swing thereof is slower and dies out more quickly. In some instances the signal transmitted by the arm 45 through the line 47 to the amplifier 21 may be such as to cause the carriage 11 to move beyond the position for which the position control 23 is set. The unbalanced condition between the position control 23 and the position' transducer 24 will then restorethe carriage to the desired position.

The steps between the Wires in the potentiometers 23, 24, and 26 may be made very small so that the automatic servo system of Fig. 1 is essentially a continuous system.

In the modification of the apparatus of the present invention illustrated in Fig. 2, the swing-angle transducer takes the form of a tachometer generator 50 the output of which is delivered through the line 47 to the amplifier 21. The generator 50 is grounded as indicated at 51 and is driven by the follower 43 through a large gear 52 secured to the follower shaft 44 and a small gear 53 coupled to the generator 50. The strength of the signal trans mitted by the generator 50 through the line 47 to the amplifier is proportional to the speed of the generator, and this speed is in turn proportional to the angle by which the cable 13 deviates from the vertical as it swings. The generator 50 is stepless and continuously transmits a signal.

The intention is to limit the invention only within the scope of the appended claims.

What is claimed is:

1. In combination, a carriage adapted to move along an elevated track, a flexible member depending from the carriage and adapted to support well below the carriage an object to be moved by movement of the carriage along the track, a control potentiometer adapted to be manually set for a position to which the carriage is to move, a location potentiometer responsive to position of the carriage, a tachometer generator, an amplifier, a source of power means electrically connecting the potentiometers and the tachometer generator with the amplifier and the source of electrical power for transmitting electrical signals to the implifier, a swing potentiometer responsive to angle of the flexible member to the vertical, means electrically connecting the swing potentiometer with the source of power and the amplifier, for transmitting an electrical signal to the amplifier, a motor and means for driving the motor from the amplifier in accordance with the aforementioned signals transmitted thereto, whereby the swing of the flexible member is reduced to zero when the carriage has reached its intended position and the swing is greatly reduced in magnitude when the carriage is being moved to its intended position.

2. In an assembly a combination comprising a movable carriage, a flexible element depending from the carriage for supporting an object to be moved by the carriage, a motor for moving the carriage, an amplifier for operating the motor, means for transmitting electrical signals to the amplifier responsive to the actual position, the intended position, and the speed of the carriage, and means responsive to the angle of the flexible element to the vertical for transmitting an electrical signal to the amplifier to modify the eflfect of the previously mentioned electrical signals upon the amplifier.

3. In an assembly a combination comprising a movable carriage, a flexible element depending from the carriage for supporting an object to be moved by the carriage, a motor for moving the carriage, an amplifier for operating the motor, means for transmitting electrical signals to the amplifier responsive to the actual position and the intended position, and means responsive to swinging of the flexible element for transmitting an electrical signal to the amplifier to modify the eifect of the previously mentioned electrical signals upon the amplifier.

4. In an assembly a combination comprising a movable carriage, a flexible element depending from the carriage for supporting an object to be moved by the carriage, a motor for moving the carriage, an amplifier for operating the motor, means for transmitting electrical signals to the amplifier responsive to the actual position, the intended position, and the speed of the carriage, and means responsive to the speed of swing of the flexible element for transmitting an electrical signal to the amplifier to modify the eifect of the previously mentioned electrical signals upon the amplifier.

No references cited. 

